it's airing tonight on pbs, and the book is called "half the sky. our soledad o'brien spoke with the authors this morning. "new york times" columnist nicolas krzysztof and laura ladone. she was asked what the inspiration was for the book. >> well, it really started many, many years ago when we were in china, and we had found out we saw students killed on campus, which was a horrible thing, but the next year when we went to the country side, we started discovering that there were 30 million missing female girls -- female babies from the chinese population, which was a stunning number. partly -- >> 30 million? >> partly through infanticide. some mothers abort female fetuses when he they found out it's a female. we thought it was just china, and so, you know, this is -- china say big complicated country. we moved to japan, and we started discovering a lot of discrimination against women there as well in japan and korea and went down to cambodia and discovered sex trafficking. we thought this was just asia. >> you realized it's the globe. what made you